Improving crop yield from agriculturally significant plants including, among others, corn, soybean, sugarcane, rice, wheat, vegetables, and cotton, has become increasingly important. In addition to the growing need for agricultural products to feed, clothe and provide energy for a growing human population, climate-related effects and pressure from the growing population to use land other than for agricultural practices are predicted to reduce the amount of arable land available for farming. These factors have led to grim forecasts of food security, particularly in the absence of major improvements in plant biotechnology and agronomic practices. In light of these pressures, environmentally sustainable improvements in technology, agricultural techniques, and pest management are vital tools to expand crop production on the limited amount of arable land available for farming.
Insects, particularly insects within the order Lepidoptera and Coleoptera, are considered a major cause of damage to field crops, thereby decreasing crop yields over infested areas. Lepidopteran pest species which negatively impact agriculture include, but are not limited to, Helicoverpa zea, Ostrinia nubilalis, Diatraea saccharalis, Diatraea grandiosella, Anticarsia gemmatalis, Spodoptera frugiperda, Spodoptera exigua, Agrotis ipsilon, Trichoplusia ni, Chrysodeixis includens, Heliothis virescens, Plutella xylostella, Pectinophora gossypiella, Helicoverpa armigera, Elasmopalpus lignosellus, Striacosta albicosta and Phyllocnistis citrella. Coleopteran pest species which negatively impact agriculture include, but are not limited to, Agriotes spp., Anthonomus spp., Atomaria linearis, Chaetocnema tibialis, Cosmopolites spp., Curculio spp., Dermestes spp., Diabrotica spp., Epilachna spp., Eremnus spp., Leptinotarsa decemlineata, Lissorhoptrus spp., Melolontha spp., Orycaephilus spp., Otiorhynchus spp., Phlyctinus spp., Popillia spp., Psylliodes spp., Rhizopertha spp., Scarabeidae, Sitophilus spp., Sitotroga spp., Tenebrio spp., Tribolium spp. and Trogoderma spp., particularly when the pest is Diabrotica virgifera virgifera (Western Corn Rootworm, WCR), Diabrotica barberi (Northern Corn Rootworm, NCR), Diabrotica virgifera zeae (Mexican Corn Rootworm, MCR), Diabrotica balteata (Brazilian Corn Rootworm (BZR), Diabrotica undecimpunctata howardii (Southern Corn Rootworm, SCR) and a Brazilian Corn Rootworm complex (BCR) consisting of Diabrotica viridula and Diabrotica speciosa).
Historically, the intensive application of synthetic chemical insecticides was relied upon as the pest control agent in agriculture. Concerns for the environment and human health, in addition to emerging resistance issues, stimulated the research and development of biological pesticides. This research effort led to the progressive discovery and use of various entomopathogenic microbial species, including bacteria.
The biological control paradigm shifted when the potential of entomopathogenic bacteria, especially bacteria belonging to the genus Bacillus, was discovered and developed as a biological pest control agent. Strains of the bacterium Bacillus thuringiensis (Bt) have been used as a source for proteins which exhibit pesticidal activity since it was discovered that Bt strains show a high toxicity against specific insects. The main feature of Bt's is the production of parasporal bodies which contain one or more crystals that contain specific insecticidal endotoxins (Cry proteins) which act upon ingestion by a susceptible insect through a pore-forming mechanism of action detrimental for the insect gut epithelium. Besides Bt, other Bacillus species, such as Bacillus sphaericus, and other bacteria species that contain genes that contribute to an entomopathogenic phenotype, such as Brevibacillus laterosporus, have shown potential for pest management.
Insecticidal toxin proteins have been employed in various agricultural applications to preserve agriculturally important plants and increase yields. Insecticidal toxin proteins are used to control agriculturally-relevant pests of crop plants by mechanical methods, such as spraying to disperse microbial formulations containing various bacteria strains onto plant surfaces, and by using genetic transformation techniques to produce transgenic plants and seeds expressing insecticidal toxin protein.
The use of transgenic plants expressing insecticidal toxin proteins has been globally adapted. For example, in 2012, 26.1 million hectares were planted with transgenic crops expressing Bt toxins (James, C., Global Status of Commercialized Biotech/GM Crops: 2012. ISAAA Brief No. 44). The expanded use of transgenic insect-protected crops and the limited number of commercially available insecticidal toxin proteins is creating a selection pressure for alleles that impart resistance to the currently-utilized insecticidal proteins. The development of resistance in target pests to insecticidal toxin proteins undermines the effectiveness and advantages of this technology. Such advantages include increased crop yields, reduction in chemical pesticide use, and reduction in the costs and labor associated with chemical pesticide use.
The discovery and development of new forms of insecticidal toxin proteins is central to managing the increase in insect resistance to transgenic crops expressing insecticidal toxin proteins. New protein toxins with improved efficacy and which exhibit control over a broader spectrum of susceptible insect species will reduce the number of surviving insects which can develop resistance alleles. In addition, two or more transgenic toxins toxic to the same insect pest and displaying different modes of action in one plant further reduces the probability of resistance in a target insect species.
Consequently, there is a critical need to discover and develop effective insecticidal proteins with improved insecticidal properties such as increased efficacy against a broader spectrum of target insect pest species and different modes of action compared to proteins known in the art. A novel protein toxin family from Brevibacillus laterosporus (B. laterosporus) is disclosed in this application along with similar toxin proteins, variant proteins, and exemplary recombinant proteins that exhibit insecticidal activity against significant target Lepidopteran and Coleopteran pest species, particularly against Western Corn Rootworm.